India's counterterrorism teams had another rude surprise Saturday when two explosions outside a cricket stadium in Bangalore injured 17 people—nine of them policemen. The explosions raise serious questions about the Congress Party's progress in anticipating and preventing domestic terrorist attacks.

The government had been warned of Saturday's strike, which occurred before the start of an Indian Premier League cricket match. In February, Ilyas Kashmiri, a Pakistani terrorist with ties to al Qaeda, warned of new terrorist strikes in India directed against the IPL and the Commonwealth Games due later this year. Security for the IPL tournament was tightened up and the Indian government assured nervous Commonwealth officials that the terrorists would not be allowed to succeed.

So far, no group has claimed responsibility for the violence, but the way the bombing was carried out suggests a local signature. The most likely suspect is the Indian Mujahideen, which organized a series of explosions in 2007 and 2008 in cities, including Bangalore and the tourist mecca of Jaipur. The group is also suspected of carrying out the Pune blast in February, which killed 17 people. No arrests have yet been made in that investigation.

Saturday's attack, combined with the as yet unresolved Pune bombing, has called into question the effectiveness of the measures taken by Home Minister Palaniappan Chidambaram to revamp the antiterror investigation machinery. Since taking office after the November 2008 Mumbai terrorist attacks, Mr. Chidambaram has set up a National Investigation Agency to improve the investigation of terrorist attacks and the prosecution of terrorists.

The government contends it has prevented a large number of other terrorist attacks of which the public has no knowledge, and that authorities are now in a better position to prevent a repeat of the Mumbai massacre. Police successfully defused a bomb in Bangalore Saturday, and three more unexploded devices Sunday. But their failure to detect the two bombs planted Saturday by the terrorists near the stadium's entrance gates is likely to increase public skepticism of the government's efforts.

To be fair, Mr. Chidambaram is trying to strengthen India's counterterrorism machinery after a long period of neglect under his predecessor, Shivraj Patil. It will take time for the results to be seen.

But Mr. Chidambaram must do more than just strengthen the government's antiterror machinery. This is only one aspect of the problem. He must also act aggressively to counter the radicalization of Indian Muslims. While the intelligence and security agencies enjoy a free hand in dealing with foreign terrorists on Indian soil, they often find their hands tied when faced with Indian terrorists, such as the Indian Mujahideen. These homegrown terrorists often have local grievances, or were turned at the instigation of Pakistani intelligence agencies and terrorist organizations.

This is a tough task. India has the second largest Muslim community in the world after Indonesia and the Indian Muslims constitute an important voter base. In many northern states, where the Congress Party dominates, the Muslim vote is crucial for victory.

While Indian Muslims support the actions of the intelligence and security agencies against Pakistani terrorists, they often protest when the government takes action against their own community, making it hard for authorities' to conduct thorough investigations. That is why the success rate in the investigation and prosecution of Pakistani terrorists is high, but low in the case of Indian Muslims involved in terrorism.

It is important for Mr. Chidambaram and the rest of the Congress Party-led government to address Muslims' legitimate grievances. But it is equally important to give security agencies a free hand in dealing with Indian Muslims who take to terrorism, by giving the authorities the additional legal powers they need for successful investigation and prosecution. If this isn't done, Saturday's bombing won't be the last.

Mr. Raman served in India's external intelligence agency from 1968 to 1994 and on the government of India's National Security Advisory Board from 2000 to 2002. He is currently director of the Institute for Topical Studies in Chennai.

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